Ablation catheter with dedicated fluid paths and needle centering insert

ABSTRACT

An irrigated needle electrode ablation catheter has a distal tip section with a tip electrode, a needle electrode assembly longitudinal movable relative to the catheter, and a needle centering insert in a channel in the tip electrode. The assembly has a proximal tubing and a distal needle electrode, and the insert supports the needle electrode in the channel at a predetermined separation distance from the tip electrode while enabling irrigation to flow circumferentially around the needle electrode through the channel and exit at the distal end of the tip electrode. The catheter also provides a first dedicated fluid pathway through the assembly and exits at the distal end of the needle electrode, and a second dedicated fluid pathway to supply fluid to the channel in the tip electrode, wherein the second pathway is defined by a guide tube and directed by a plunger member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/256,876, filed Apr. 18, 2014, the entire content of which isincorporated herein by reference.

FIELD OF INVENTION

This invention relates to catheters, in particular, cardiac cathetersfor ablation and tissue diagnostics.

BACKGROUND

Radiofrequency (RF) ablation of cardiac and other tissue is a well-knownmethod for creating thermal injury lesions at the tip of an electrode.Radiofrequency current is delivered between a skin (ground) patch andthe electrode. Electrical resistance at the electrode-tissue interfaceresults in direct resistive heating of a small area, the size of whichdepends upon the size of the electrode, electrode tissue contact, andcurrent (density). Further tissue heating results from conduction ofheat within the tissue to a larger zone. Tissue heated beyond athreshold of approximately 50-55 degrees C. is irreversibly injured(ablated).

Resistive heating is caused by energy absorption due to electricalresistance. Energy absorption is related to the square of currentdensity and inversely with tissue conductivity. Current density varieswith conductivity and voltage and inversely with the square of radiusfrom the ablating electrode. Therefore, energy absorption varies withconductivity, the square of applied voltage, and inversely with thefourth power of radius from the electrode. Resistive heating, therefore,is most heavily influenced by radius, and penetrates a very smalldistance from the ablating electrode. The rest of the lesion is createdby thermal conduction from the area of resistive heating. This imposes alimit on the size of ablation lesions that can be delivered from asurface electrode.

Methods to increase lesion size would include increasing electrodediameter, increasing the area of electrode contact with tissue,increasing tissue conductivity and direct mechanical penetration of thetissue by the ablating electrode/needle.

The electrode can be introduced to the tissue of interest directly (forsuperficial/skin structures), surgically, endoscopically,laparoscopically or using percutaneous transvascular (catheter-based)access. Catheter ablation is a well-described and commonly performedmethod by which many cardiac arrhythmias are treated. Needle electrodeshave been described for percutaneous or endoscopic ablation ofsolid-organ tumors, lung tumors, and abnormal neurologic structures.

Catheter ablation is sometimes limited by insufficient lesion size.Ablation of tissue from an endovascular approach results not only inheating of tissue, but heating of the electrode. When the electrodereaches critical temperatures, denaturation of blood proteins causescoagulum formation. Impedance can then rise and limit current delivery.Within tissue, overheating can cause steam bubble formation (steam“pops”) with risk of uncontrolled tissue destruction or undesirableperforation of bodily structures. In cardiac ablation, clinical successis sometimes hampered by inadequate lesion depth and transverse diametereven when using catheters with active cooling of the tip. Theoreticalsolutions have included increasing the electrode size (increasingcontact surface and increasing convective cooling by blood flow),improving electrode-tissue contact, actively cooling the electrode withfluid infusion, changing the material composition of the electrode toimprove current delivery to tissue, and pulsing current delivery toallow intermittent cooling.

Needle electrodes improve contact with tissue and allow deep penetrationof current delivery to areas of interest. Ablation may still be hamperedby the small surface area of the needle electrode such that heatingoccurs at low power, and small lesions are created. An improved catheterwith needle ablation is disclosed in U.S. Pat. No. 8,287,531, the entiredisclosure of which is hereby incorporated by reference.

While needle electrodes improve tissue ablation, the structuralintegrity of a needle electrode may be compromised by steam pops arisingfrom RF “arcing” between the needle electrode and adjacent conductivecomponents of the catheter, including a tip electrode through which theneedle electrode extends. When electrical conduction occurs between theneedle electrode and the distal end of the tip electrode, the resultingcavitation or mini-shockwaves produced by the steam pops can causepremature wear and tear on the needle electrode that could lead tobreakage and detachment from the catheter.

The “arcing” may be reduced by increasing the distance, especially theradial distance, between the needle electrode and the tip electrode.However, by increasing the distance, the formation of coagulum betweenthe needle electrode and the tip electrode may increase despitesurrounding blood flow that typically tends to minimize or preventcoagulum formation.

Accordingly, it is desirable for a catheter to have a distal tipconfiguration that increases distance, especially radial distance,between the needle electrode and the tip electrode, and providesirrigation between the needle electrode and the tip electrode,especially at the distal end of the tip electrode, to minimize theformation of coagulum. It is also desirable that the irrigation besupplied by a dedicated fluid path with sufficient pressure so as toavoid blood seepage into the catheter while minimizing the risk oftrapped air bubbles. It is further desired that the irrigation besupplied circumferentially around the outer surface of the needleelectrode for uniform cooling.

SUMMARY OF THE INVENTION

The catheter of the present invention is directed to an improvedcatheter with an elongated catheter body, a distal tip section with atip electrode, a needle electrode assembly configured for longitudinalmovement relative to the catheter, and a needle centering insert that isreceived in a channel formed in the tip electrode. The needle electrodeassembly has a proximal tubing and a distal needle electrode, and theinsert is advantageously configured to support the needle electrode inthe channel of the tip electrode at a predetermined separation distancefrom the tip electrode while enabling irrigation to flowcircumferentially around the needle electrode through the channel andexit at the distal end of the tip electrode for uniform cooling andminimizing the formation of coagulum on the distal end of the tipelectrode.

The catheter also provides a first dedicated pathway that extendsthrough the needle electrode assembly and exits at the distal end of theneedle electrode for passing fluid along the catheter and directly intotissue at the needle electrode ablation site. The catheter also providesa second dedicated pathway to supply fluid to the channel in the tipelectrode, wherein the second pathway is defined by a guide tube anddirected by a plunger member. The guide tube surrounds the needleelectrode assembly throughout its length and is sized to provide a gapwith an annular cross-section between the inner surface of the guidetube and the outer surface of the proximal tubing. The plunger member isfixedly positioned on the proximal tubing to maintain a fluid-tight sealwith the inner surface of the guide tubing for directing the flowdistally, as the needle electrode assembly is extended or retractedlongitudinally relative to the catheter. To supply fluid to the annulargap, the second pathway includes a traversal from a lumen in theproximal tubing to the annular gap via a hole formed in the sidewall ofthe proximal tubing. The location of the plunger member on the proximaltubing is immediately proximal of the hole so as to minimize the risk oftrapped air bubbles forming in the second pathway. The first and secondfluid pathways are advantageously dedicated and independent of eachother so as to assure that the fluid passing through each pathway has aconstant flow regardless of whether the needle electrode is extended andinsert into tissue or retracted into the tip electrode.

In one embodiment, the catheter comprises an elongated catheter body, adistal tip section having a tip electrode with a needle channel, aneedle centering insert having a needle passage, the insert positionedin the needle channel of the tip electrode, and a needle electrodeassembly having a proximal tubing extending through at least a lumen inthe elongated catheter body and a distal needle electrode extendingthrough the needle passage of the insert, and an injection controlhandle configured to move the needle electrode assembly into theextended position and the retracted position, wherein the needle passagehas an inner surface with at least one groove configured for fluid flowbetween the insert and the needle electrode extending through the needlechannel. The catheter further comprises a fluid path that communicateswith the at least one groove, wherein the fluid path has a distal exitat the distal end of tip electrode. The catheter may also comprise asecond fluid path extending through at least the catheter body andhaving a distal exit at the distal end of the needle electrode assembly,wherein the first and second fluid paths are isolated from each other.

In a more detailed embodiment, the needle electrode assembly includes aproximal tubing and a distal needle electrode, and the second fluid pathpasses through the proximal tubing and the distal needle electrode.

In another embodiment, the catheter comprises an elongated catheterbody, a distal tip section having a tip electrode with a distal end, aneedle electrode assembly extending through at least the elongatedcatheter body and the tip electrode, the needle electrode assembly beinglongitudinally movable relative to the catheter body and distal tipsection into an extended position and a retracted position, and aninjection control handle proximal of the catheter body configured tomove the needle electrode assembly into the extended position and theretracted position. The catheter further comprises a first fluid pathextending through at least the catheter body and having a distal exit atthe distal end of the tip electrode, and a second fluid path extendingthrough at least the catheter body and having a distal exit at thedistal end of the needle electrode assembly, wherein the first andsecond fluid paths are isolated from each other.

In a more detailed embodiment, the needle electrode assembly of thecatheter has an elongated proximal tubing extending through the catheterbody, and a distal needle electrode extending through the tip electrode.The catheter also has a needle centering insert, wherein the tipelectrode has a longitudinal passage that receives the needle centeringinsert, the needle centering insert having a needle passage throughwhich needle electrode extends. An inner surface of the insert liningthe needle passage has a cross-section with a smaller diameter forming apeak and a larger diameter forming a valley, wherein the peak supportsthe needle electrode in the needle passage and the valley allows fluidto pass along the outer surface of the needle electrode.

In a more detailed embodiment, the catheter includes a guide tube thatsurrounds the needle electrode assembly along its length, but sized toleave a gap with an annular cross-section between the assembly and theguide tube. The first fluid path passes through the needle electrodeassembly. The second fluid path has a proximal portion that extendsthrough the needle electrode assembly, a distal portion that extendsthrough annular gap, and a traversal portion that connects the proximalportion and the distal portion via hole in the side wall of the needleelectrode assembly.

In a more detailed embodiment, the needle electrode assembly includes aproximal tubing having a plunger member on its outer surface that formsa seal against an inner surface of the guide tube, wherein the plumbermember maintains the seal as the needle electrode assembly moveslongitudinally relative to the catheter body.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view of a catheter of the present invention, inaccordance with one embodiment.

FIG. 2A is a side cross-sectional view of the catheter of FIG. 1,including a junction between a catheter body and the deflection section.

FIG. 2B is a side cross-sectional view of the catheter of FIG. 1,including a junction between the catheter body and the deflectionsection, along a second diameter generally perpendicular to the firstdiameter of FIG. 2A.

FIG. 2C is an end cross-sectional view of the deflection section ofFIGS. 2A and 2B, taken along line C-C.

FIG. 3A is a side cross-sectional view of a distal tip section of thecatheter of FIG. 1, including a needle electrode assembly of the presentinvention in an extended position, taken along the first diameter.

FIG. 3B is a side cross-sectional view of the distal tip section of FIG.3A, including the needle electrode assembly in a retracted position.

FIG. 3C is the side cross-sectional view of the distal tip section ofFIGS. 3A and 3B, taken along the second diameter.

FIG. 3D is an end cross-sectional view of the distal tip section ofFIGS. 3A, 3B and 3C, taken along line D-D.

FIG. 3E is a detailed view of a junction between a deflection sectionand a tip electrode of FIG. 3A.

FIG. 4A(1) is a perspective view of a needle centering insert, inaccordance with one embodiment of the present invention.

FIG. 4A(2) is another perspective view of the needle centering insertFIG. 4A(1).

FIG. 4B is an end cross-sectional view of the needle centering insert ofFIG. 4A(1) taken along line 4B-4B.

FIG. 4C is an end cross-sectional view of the needle centering insert ofFIG. 4A(2) taken along line 4C-4C.

FIG. 5 is a side cross-sectional view of a deflection control handle, inaccordance with one embodiment of the present invention.

FIG. 6 is a side cross-sectional view of a needle injector controlhandle, in accordance with one embodiment of the present invention,taken along a first diameter.

FIG. 6A is a detailed view of the needle injector control handle,including the needle electrode assembly, of section A of FIG. 6.

FIG. 6B is a side cross-sectional view of a needle injector controlhandle of FIG. 6, taken along a second diameter.

FIG. 6C is an end cross-sectional view of the needle injector controlhandle, including the needle electrode assembly taken along line C-C.

FIG. 6D is an end cross-sectional view of the needle injector controlhandle, including the needle electrode assembly taken along line D-D.

FIG. 6E is an end cross-sectional view of the needle injector controlhandle, including the needle electrode assembly taken along line E-E.

FIG. 7 is a detailed view of the needle injector control handle,including guiding and supporting structures for the needle electrodeassembly, of section X of FIG. 6.

FIG. 8 is a detailed view of the needle injector control handle,including distal portion of a luer connector and fluid supply luertubings, of section Y of FIG. 6

FIG. 9 is a side, partial cross-sectional view of luer hubs connected tothe needle injector control handle, in accordance with one embodiment.

FIG. 10 is a perspective view of a distal end of the catheter, includingan extended needle electrode, in accordance with one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, the catheter 100 comprises an elongated catheterbody 112, an intermediate deflection section 114, a distal tip section115, a deflection control handle 116 attached to the proximal end of thecatheter body 112, and a needle injector control handle 117 attachedindirectly to the catheter body 112 proximal of the deflection controlhandle 116.

With reference to FIGS. 2A and 2B, the catheter body 112 comprises asingle, central or axial lumen 118. The proximal shaft 112 is flexible,i.e., bendable, but substantially non-compressible along its length. Thecatheter body 112 may be of any suitable construction and made of anysuitable material. In one embodiment, the catheter body 112 comprises anouter wall 26 made of PEBAX®, polyurethane or nylon. The outer wall 26comprises an imbedded braided mesh of stainless steel or the like toincrease torsional stiffness of the catheter body 112 so that, when thedeflection control handle 116 is rotated, the catheter body 112 and thedistal remainder of the catheter rotate in a corresponding manner.

The outer diameter of the catheter body 112 is not critical, but in oneembodiment it is preferably no more than about 8 French. Likewise thethickness of the outer wall 26 is not critical. In the depictedembodiment, the inner surface of the outer wall 26 is lined with astiffening tube 20, which can be made of any suitable material,preferably polyimide. The stiffening tube 20, along with the braidedouter wall 26, provides improved torsional stability while at the sametime minimizing the wall thickness of the catheter, thus maximizing thediameter of the single lumen. The outer diameter of the stiffening tube20 is about the same as or slightly smaller than the inner diameter ofthe outer wall 26.

As shown in FIGS. 2A, 2B and 2C, the intermediate deflection section 114comprises a shorter section of multi-lumened tubing 19 having, forexample, at least four lumens, namely a first lumen 121, a second lumen122, a third lumen, and a fourth lumen 124, most if not all of which areoff-axis. The tubing 19 is made of a suitable non-toxic material that ispreferably more flexible than the catheter body 12. A suitable materialfor the tubing 19 is braided polyurethane, i.e., polyurethane with anembedded mesh of braided stainless steel or the like. The outer diameterof the intermediate deflection section 114, like that of the catheterbody 112, is in the disclosed embodiment no greater than about 8 French.

A suitable means for attaching the catheter body 112 to the intermediatedeflection section 114 is illustrated in FIGS. 2A and 2B. The proximalend of the intermediate deflection section 114 comprises an innercounter bore 134 that receives the outer surface of the distal end ofthe stiffener 20. These ends are attached by glue or the like. Othermethods for attaching can be used in accordance with the invention.

The stiffening tube 20 is held in place relative to the outer wall 26 atthe catheter body 112. In a suitable construction of the catheter body112, a force is applied to the proximal end of the stiffening tube 20,which causes the distal end of the stiffening tube 20 to firmly pushagainst the counter bore 134. While under compression, a first gluejoint is made between the stiffening tube 20 and the outer wall 26 by afast drying glue, e.g. Super Glue®. Thereafter, a second glue joint isformed between the proximal ends of the stiffening tube 20 and outerwall 26 using a slower drying but stronger glue, e.g., polyurethane.

The depicted catheter includes a mechanism for deflecting the catheter.In the depicted embodiment, the catheter is adapted for uni-directionaldeflection with a puller wire 17 extending into the second lumen 122.The puller wire is anchored at its proximal end in the deflectioncontrol handle 116 and anchored at its distal end in the distal tipsection 115. The puller wire is made of any suitable metal, such asstainless steel or Nitinol, and is preferably coated with Teflon® or thelike. The coating imparts lubricity to the puller wire. In oneembodiment, the puller wire has a diameter ranging from about 0.006 toabout 0.010 inches.

To effectuate deflection along the deflection section 114, the pullerwire is surrounded by a compression coil 24 that extends from theproximal end of the catheter body 112 and terminates at or near theproximal end of the deflection section 114. The compression coil 24 ismade of any suitable metal, for example, stainless steel. Thecompression coil 24 is tightly wound on itself to provide flexibility,i.e., bending, but to resist compression. The inner diameter of thecompression coil 24 is preferably slightly larger than the diameter ofthe puller wire. For example, when the puller wire has a diameter ofabout 0.007 inches, the compression coil preferably has an innerdiameter of about 0.008 inches. The Teflon® coating on the puller wireallows it to slide freely within the compression coil 24. Along itslength, the outer surface of the compression coil 24 is covered by arespective flexible, non-conductive sheath to prevent contact othercomponents inside the catheter body 112. The non-conductive sheath maybe made of polyimide tubing. Each compression coil 24 is anchored at itsproximal end to the proximal end of the stiffening tube 20 in thecatheter body 112 by glue (not shown). At its distal end, thecompression coil 24 is anchored in the second lumen 122 by a glue joint.Within the deflection section 114, the puller wire 17 extends through aprotective sheath 18, for example of Teflon®, which prevents the pullerwire from cutting into the wall of the tubing 19 when the deflectionsection is 114 is deflected. Any other suitable technique for anchoringthe puller wire 17. Moreover, bi-directional deflection may be providedwith the use of a second puller wire as known in the art.

Longitudinal movement of the puller wire relative to the catheter body112, which results in deflection of the deflection section 114, isaccomplished by suitable manipulation of the control handle 16 (FIG. 1).Examples of suitable control handles manipulating a single puller wirefor unidirectional deflection are disclosed, for example, in U.S. Pat.Nos. Re 34,502, 5,897,529 and 6,575,931, the entire disclosures of whichare incorporated herein by reference. Suitable control handlesmanipulating at least two puller wires for bidirectional deflection aredescribed in U.S. Pat. Nos. 6,123,699, 6,171,277, and 6,183,463, thedisclosures of which are incorporated herein by reference.

Extending through the catheter body 112 and into the distal tip section115 is an irrigated ablation needle electrode assembly 132, as shown inFIG. 3A. The assembly 132 comprises a proximal tubing 13 and a distalelectrode needle 12. The proximal tubing 13 extends through the centrallumen 118 of the catheter body 112 and the lumen 121 of the tubing 19 ofthe deflection section 114 (FIGS. 2A and 2C). The distal electrodeneedle 12 extends through the distal tip section 115, although theassembly 132 as a whole is longitudinally movable relative to catheterbody 112 and the distal tip section 115, between a retracted, withdrawnposition (FIG. 3B) and an extended, deployed position (FIG. 3A).

As shown in FIGS. 3A, 3B and 3C, the distal tip section 115 includes atip electrode 2 and a connector tubing 4. The tip electrode 2 has alongitudinal channel 130, with a circular cross-section, through whichthe distal electrode needle 12 extends. The channel 130 has a shorterproximal portion 130P with a larger diameter, a longer distal portion130D with a smaller diameter, an annular abutment or stop 130A at ajunction therebetween.

A proximal end of the tip electrode 2 is attached to the tubing 19 ofthe deflection section 114 by the connector tubing 4 whose proximal endis mounted over a notched outer surface of the distal end of the tubing19 and whose distal end is mounted over a notched proximal end of thetip dome electrode 2. The tubing 4, which may be constructed of anysuitable material, for example, PEEK (polyimide or polyetheretherketone), has a central lumen 4L and a length that provides an axialseparation gap G between the tubing 19 and the tip electrode 2 so thatcomponents extending therebetween can bend and reorient/realign asneeded. A ring electrode 21 is mounted over connector tubing 4 and theproximal end of the tip electrode 2. An adhesive sealant 135, forexample, polyurethane, is applied to the proximal and distal ends of theconnector tubing 4 to secure attachment.

With reference to FIG. 3D, a proximal face of the tip electrode 2 isformed with multiple blind holes 141 and 142. The blind hole 141 isgenerally aligned with the lumen 124 of the deflection section 114 andreceives an electromagnetic position biosensor 16. The blind hole 142 isgenerally axially aligned with the lumen 122 of the deflection section114 and receives a distal end of the puller wire 17, including an anchor17A, for example, a stainless steel hypo stock crimped onto the distalend of the puller wire, that is soldered or otherwise potted in theblind hole 142. The blind hole 142 also receives a distal end of a leadwire 15T extending from the lumen 123 of the deflection section 114 andthe central lumen 118 of the catheter body 112. The lead wire 15T, whichis provided for the tip electrode 2, readily bends as needed in theaxial gap G between the lumen 123 and the blind hole 142.

The tip dome electrode 2 and the ring electrode 21 may be constructed ofany suitable material, including platinum, iridium, palladium or acombination thereof. Lead wire 15N is provided for the needle electrode12 and the lead wire 15R is provided for the ring electrode 21. The leadwire 15R extends from the deflection control handle 116, through thelumen 118 of the catheter body 112, and the lumen 123 of the deflectionsection 114 and into the axial gap G where its distal end is connectedto the ring electrode 21 through an opening 3 (FIG. 3B) formed in theside wall of the connector tubing 4. The path of the lead wire 15N inthe catheter is explained further below.

The needle electrode assembly 132 is used to ablate tissue whilesimultaneously injecting saline or other fluid to conduct the ablationenergy and cool the needle electrode. The saline in the perfused tissueincreases the effective size of the ablation electrode. The needleelectrode assembly 132 is extendable and retractable by manipulation ofthe needle control handle 17 (FIG. 1), as described further below. FIG.3A depicts the needle electrode assembly 132 in an extended positionrelative to the catheter as it would be to ablate and/or monitorelectrograms from the tissue. The needle electrode 12 may be returned orwithdrawn into the channel 130, as shown in FIG. 3B, to avoid damage toits distal end and/or injury to the patient, particularly while thecatheter is advanced through the vasculature of a patient's body andwhile the catheter is removed from the body.

The needle electrode assembly 132 extends through the injection controlhandle 117, the deflection control handle 116, the catheter body 112,and the deflection section 114 and into the distal tip section 115, asshown in FIG. 3A. In the disclosed embodiment, the proximal tubing 13extends from the needle control handle 117, through the deflectioncontrol handle 16, through the lumen 118 of the catheter body 112, andinto the first lumen 131 of the deflection section 114. The elongatedflexible proximal tubing 13 with lumen 13L is connected to the needleelectrode 12 which is a generally rigid, electrically-conductive tubingthat is hollow with a lumen 12L. The generally rigid nature of theneedle electrode 12 (used herein interchangeably with “electrodeneedle”) allows it to pierce tissue in order to increase itseffectiveness during ablation. In one embodiment, the needle electrode12 is formed of Nitinol or stainless steel, and, as illustrated, isformed with a beveled edge 28 at its distal tip to enhance its abilityto pierce tissue. The proximal tubing 13 may be made PEEK, but may bemade of any other suitable biocompatible material, such as plastic ormetal.

In the illustrated embodiment, the proximal tubing 13 and the needleelectrode 12 are joined whereby a proximal end of the needle electrode12 is received in the lumen 13L of the proximal tubing 13 at its distalend. As such, the lumen 13L of the proximal tubing 13 communicates withand is directly connected to the lumen 12L of the needle electrode 12.Fluid in the lumen 13L can therefore pass into the lumen 12L and exitfrom the catheter at the distal end of the needle electrode 12 as shownby arrows A. As described further below, the fluid shown by arrows Apasses along a first isolated, independent and dedicated fluid pathway,defined in part by the lumen 13L of the proximal tubing 13 and the lumen12L of the needle electrode 12. The first fluid path extends from theinjection control handle 117, through the deflection control handle 116,and through lumens in the catheter body 112, the deflection section 114and the needle electrode 12.

As shown in FIGS. 3A, 3B and 3E, the lead wire 15N provided for theneedle electrode 12 extends through the proximal tubing 13. In thedistal end of the proximal tubing 13, a distal portion of the lead wire15N is coiled and soldered around a proximal portion of the needleelectrode 12, wherein the coiled lead wire and the proximal portion ofthe needle electrode are potted and anchored in the distal end of theproximal tubing 13 by a suitable material, for example, polyurethane135. The inner diameter of the proximal tubing 13 is sized toaccommodate the windings of the lead wire 15N around the proximalportion and surrounding sealant 135. The windings and the sealanttogether form a fluid-tight sealed joint which securely anchors theelectrode needle 12 to the proximal tubing 13. The fluid designated byarrows A is therefore wholly contained within the needle electrodeassembly 132 along its entire length, and this pathway is open andavailable before, during and after any and all longitudinal movement ofthe needle electrode assembly 132 relative to the catheter in extendingand retracting the electrode needle 12.

In accordance with another feature of the present invention, the distaltip section 115 includes a needle centering insert 90 that is fixedlysituated in the channel 130 to position and center the needle electrode12 on-axis within the channel 130, the significance of which isexplained further below. As shown in FIGS. 4A(1) and 4A(2), the insert90 has a generally elongated cylindrical body defining an outer diameterOD. On the outer surface of the insert 90, a raised formation or ring 92is provided at a predetermined location along the longitudinal axis ofthe insert closer to the proximal end of the body. The ring 92 isadapted and configured to abut with the stop 130A (FIG. 3A) of thechannel 130 of the tip electrode 2 as a safety measure to prevent theinsert 90 from slipping out and dislodging from the tip electrode.

The cylindrical body of the insert 90 has a centered, on-axis needlepassage 91 which defines an inner diameter ID. The needle electrode 12extends in and through the needle passage 91. Glued within the channel130, the outer diameter OD of the insert 90 (as accommodated by thediameter of the channel 130) advantageously provides the desirableradial distance or separation R (FIG. 3A) between the needle electrode12 and the tip electrode 2, especially at the latter's distal face 2D soas to reduce or minimize electrical “arcing” between the proximal edgeof the exposed portion of the needle electrode 12 (extending distallyoutside of the tip dome electrode) and the distal face 2D when theneedle electrode 12 is energized. As such, the insert 90 is made of anonconductive material, such as PEEK.

In accordance with a feature of the present invention, the inner surfaceof the insert 90 lining the needle passage 91 has a cross-section withat least a portion with a smaller diameter that supports the needleelectrode 12 centered and on-axis with the needle passage 91 and atleast a portion with a larger diameter that provides at least onelongitudinal fluid pathway through the needle passage 91 between theinner surface of the insert and the outer surface of the needleelectrode 12. In the disclosed embodiment, the inner surface of theinsert 90 has an uneven or undulating pattern formed with the largerdiameter D1 and the smaller diameter D2 alternating each other about thelongitudinal axis of the insert (FIG. 4B), forminglongitudinally-spanning peaks P (axial ridges) and valleys V (axialgrooves) that run the length of the insert 90 between its distal andproximal ends, as shown in FIGS. 4A(1) and 4A(2). The peaks P are sizeduniformly in the radial direction so they provide uniform andsimultaneous circumferential support to the needle electrode 12 in orderto keep the needle electrode centered and on-axis in the channel 130.The valleys V allow fluid, e.g., saline, to pass distally into thechannel 130 along the outer surface of the needle electrode 12, as shownby arrows B (FIGS. 3B and 6A), forming a generally circumferential“sleeve of saline” surrounding the outer surface of the needle electrode12, and out of the tip dome electrode 2 at the distal face 2D where thesleeve of saline advantageously minimizes the formation of coagulum atthe proximal edge E of the exposed needle electrode 12 (FIG. 10). In thedisclosed embodiment, the insert 90 is formed with a plurality of sixpeaks and six valleys evenly distributed in the radial direction. It isunderstood that the plurality of peaks and valleys may vary as needed orappropriate, for example, each ranging between about three and nine.Moreover, the proximal face of the insert 90 is formed with at least oneindented formation or groove 29 (FIGS. 4A(2) and 4C) extending radiallyand providing communication between at least one valley V and the outersurface of the insert 90 so that fluid can continue to flow from thelumen 13L into the needle passage 91 when the needle assembly 132 isfully extended distally and the distal end of the proximal tubing 13abuts against the proximal face of the insert 90.

To supply fluid to at least one valley V along the passage 91 betweenthe inner surface of the insert 90 and the outer surface of the needleelectrode 12, the catheter 100 includes a first elongated fluid-tightguide tubing 22 (FIGS. 2C, 3A and 3B), with lumen 22L, that surroundsthe proximal tubing 13 generally along its entire length between theinjection control handle 117 and the needle electrode 12 but is sized toleave a gap with an annular cross-section between its inner surface andthe outer surface of the proximal tubing. The sidewall of the guidetubing 22 provides a fluid tight seal along the length of the proximaltubing 13 in the injection control handle 117, the deflection controlhandle 116, the catheter body 112 and the deflection section 114. Adistal end of the fluid-tight tubing 22 is mounted over the proximal endof the insert 90 and abuts with the proximal face of the ring 92 of theinsert 90. Accordingly, with the insert 90 being affixed in the tipelectrode 2, the guide tubing 22 is not afforded longitudinal movementrelative to the catheter and does not slide with the needle electrodeassembly 132. That is, the guide tubing 22 remains stationary relativeto the catheter as the needle electrode assembly 132 is extended andretracted through the lumen 22L of the guide tubing 22. An adhesivesealant 135, for example, Polyurethane, is applied to seal the distalend of the guide tubing 22 to the ring 92 of the insert 90 which locksthe guide tubing 22 at its distal end to the insert 90 and the tipelectrode 2.

The guide tubing 22 surrounding the proximal tubing 13 extends throughthe lumen 121 (FIGS. 2A and 2C) of the tubing 19 of the deflectionsection 114 and the lumen 118 of the catheter body 112. The guide tubing22 further extends through the deflection control handle 116 andterminates at its proximal end in the injection control handle 117. Inthe injection control handle 117, the guide tubing 22 is surrounded by ashorter protective tubing 25, made of, for example, polyamide nylon orZYTEL, that surrounds the guide tubing 22 in the needle control handle117. The protective tubing 25 is glued to the guide tubing 22 and thusis also stationary relative to the control handle 117. Accordingly, thefluid shown by arrows B passes along a second isolated, independent anddedicated second fluid pathway, defined by the annular gap in the lumen22L between the guide tubing 22 and the proximal tubing 13, the grooves29 on the proximal face of the insert 90, and the valleys V of theinsert 90 (FIG. 3B). The second fluid path extends from the injectioncontrol handle 117, through the deflection control handle 116, thecatheter body 112, the deflection section 114 and the distal tipelectrode 2. The fluid designated by arrows B is therefore containedwithin the guide tubing 22 and the insert 90, and this pathway isgenerally unaffected and undisturbed by either longitudinal movement ofthe needle electrode assembly 132 or by the first pathway designated byarrows A defined in the needle electrode assembly 132, as describedabove. In accordance with a feature of the present invention, each ofthe first and second pathways is generally separate and independent ofeach other.

Longitudinal movement of the puller wire 17 relative to the catheter,which results in deflection of the deflection section 114 isaccomplished by suitable manipulation of the control handle 16. As shownin FIG. 5, the distal end of the control handle 16 comprises a barrel53, a piston 54 with a thumb control 56 longitudinally slidable in thebarrel 53 for manipulating the puller wire 17. The proximal end of thecatheter body 112 is connected to the piston 54 by means of a shrinksleeve 58.

Components including the puller wire 17, the lead wires 15T, 15N and15R, the electromagnetic sensor cable 16C, and the proximal tubing 13along with the components passing therethrough extend through the piston54. The puller wire 17 is anchored to an anchor pin 57 located proximalof the piston 54. The lead wires 40 and electromagnetic sensor cable 74extend through a first tunnel 58, located near the side of the controlhandle 16. The electromagnetic sensor cable 16C connects to the circuitboard 64 near the proximal end of the control handle 116. Wires 73connect the circuit board 64 to a computer and imaging monitor (notshown) via an electrical connector 48.

The proximal tubing 13 of the needle assembly 132 extends through aguide tube 66 at the proximal end of the deflection control handle 116and is afforded longitudinal movement therein. The guide tube 66 is madeof any suitable material, for example, polyurethane, and is anchored tothe piston 54 in the first tunnel 58, for example, by a glue joint. Thisdesign allows the needle assembly 132 longitudinal movement within thecontrol handle 116 so that the needle assembly 132 does not break whenthe piston 54 is adjusted to manipulate the puller wire 17. Within thepiston 54, the electromagnetic sensor cable 16C and lead wires 15 passthrough a transfer tube and the puller wire 17 passes through anothertransfer tube to allow longitudinal movement of these components throughthe glue joint in the first tunnel 58.

The proximal tubing 13 of the needle assembly 132 and guide tube 66extend through a second tunnel 60 situated near the side of the controlhandle 116. To avoid undesirable bending of the needle assembly 132, aspace 62 is provided between the proximal end of the piston 54 and thedistal end of the second tunnel 60. In one embodiment, the space 62 hasa length of at least 0.50 inch and more preferably about from about 0.60inch to about 0.90 inch.

In the proximal end of the control handle 116, the proximal tubing 13,and guide tube 66 extend through a second larger plastic guide tube 68,made of, for example, Teflon®, which affords the guide tube 66 and theproximal tubing 13 longitudinal slidable movement. The second guide tube68 is anchored to the inside of the control handle 116 by glue or thelike and extends proximally beyond the control handle 116. The secondguide tube 68 protects the proximal tubing 13 both from contact with thecircuit board 64 and from any sharp bends as the guide tube 66 and theproximal tubing 13 emerge from the control handle 116. A suitabledeflection control handle is described in U.S. Pat. No. 6,623,474, theentire disclosure of which is hereby incorporated by reference.

Extension and retraction of the needle assembly 132 out the distal endof the tip electrode 2 is accomplished by the needle injection controlhandle 117. As illustrated in FIG. 6, the needle control handle 117comprises a generally cylindrical outer body 80 having proximal anddistal ends, a piston chamber 82 extending a part of the waytherethrough, and a passage 83 extending a part of the way therethrough.The piston chamber 82 extends from the proximal end of the handle partway into the body 80, but does not extend out the distal end of thebody. The passage 83, which has a diameter less than that of the pistonchamber 82, extends from the distal end of the piston chamber to thedistal end of the outer body 80.

A piston 84, having proximal and distal ends, is slidably mounted withinthe piston chamber 82. A luer connector 86 is mounted in the proximalend of the piston 84. The luer connector 86 is made of a rigid material,for example, stainless steel. The piston 84 has an axial passage 85through which the proximal tubing 13 of the needle assembly 132 extends,as described in more detail below. A compression spring 88 is mountedwithin the piston chamber 82 between the distal end of the piston 84 andthe outer body 80.

As shown in FIGS. 6 and 7, the proximal end of the proximal tubing 13 ofthe needle assembly 132 is received in lumen 87L of a rigid tubularportion 87 of the luer connector 86. The proximal end of the proximaltubing 13 of the needle assembly 132 is glued or otherwise affixed tothe overlapping inner surface of the rigid tubular portion 87 of theluer connector 86. The luer connector 86 is screwed into the piston 84so that it moves longitudinally with the piston. This arrangementcouples longitudinal movement of the luer connector 86 and the piston 84to the proximal tubing 13 and hence to the needle assembly 132, so thatlongitudinal movement of the piston 84 extends and retracts the needleassembly 132. The proximal tubing 13 and rigid tubular portion 87 extendthrough the axial passage 85 of the piston 84. Within the axial passage85, a rigid tube 93, preferably made of stainless steel, has a proximalend which is coaxial to the distal end of the rigid tubular portion 87.The rigid tube 93 is secured to the needle control handle 117. Theshorter tubing 25, glued to the guide tubing 22, is also glued to therigid tube 93. The rigid tubular portion 87 of the luer connector 86(along with the proximal tubing 13 of the needle electrode assembly 132affixed to the rigid tubular portion 87) telescopes in and out of therigid tube 93. A protective cover or shrink sleeve 97 is applied overthe rigid tube 93 to secure the loosely coiled tubing 32 to the rigidtube 93

In use, force is applied to the piston 84 to cause distal movement ofthe piston relative to the outer body 80, which compresses thecompression spring 88. This movement causes the proximal tubing 13 ofthe needle assembly 132 to correspondingly move distally relative to theouter body 80, tubings 22, 25, 93 and 97 and catheter body 112, so thatthe distal end of the needle electrode 12 outside the distal end of thetip electrode 2 (FIG. 3A). When the force is removed from the piston,the compression spring 88 pushes the piston 84 proximally to itsoriginal position, thus causing the distal end of the needle electrode12 to retract back into the tip electrode 2 (FIG. 3B). Upon distalmovement of the piston 84, the rigid tubular portion 87 moves distallyinto the rigid tube 91 to align the needle assembly 132 with thecomposite tubing 22.

The piston 84 further comprises a longitudinal slot 101 extending alonga portion of its outer edge. A set screw 102 extends through the outerbody 80 and into the longitudinal slot 100. This design limits thedistance that the piston can be slid proximally out of the pistonchamber 82. When the distal end of the needle electrode 12 is in theretracted position, the set screw 102 is typically at or near the distalend of the longitudinal slot 100.

The proximal end of the piston 84 has a threaded outer surface 104. Acircular thumb control 106 is mounted on the proximal end of the piston.The thumb control 106 has a threaded inner surface 108 that interactswith the threaded outer surface 104 of the piston. The thumb control 106acts as a stop, limiting the distance that the piston 84 can be pushedinto the piston chamber 82, and thus the distance that the needleelectrode 12 can be extended out the distal end of the catheter. Thethreaded surfaces of the thumb control 106 and piston 84 allow the thumbcontrol to be moved closer or farther from the proximal end of the outerbody 80 so that the extension distance of the needle electrode 12 can becontrolled by the user, for example, a physician. The thumb control 106also incorporates a detent feature, wherein a stainless steel ball 75 isheld in place by a spring 76 and set screw 77 so that when the thumbcontrol 106 is advanced over a metal end cap 78 at the proximal end ofthe outer body 80, the ball 75 holds the thumb control 106 in anadvanced position until additional force is used to force the ball 75over vertical step 78V (FIG. 6) of the metal end cap 78 and release thethumb control 106 from the metal end cap 78. Using the detent feature,the physician can lock the needle electrode assembly 132 in an extendedposition for the duration of an ablation. As would be recognized by oneskilled in the art, the thumb control 106 can be replaced by any othermechanism that can act as a stop for limiting the distance that thepiston 84 extends into the piston chamber 82, and it is not necessary,although it is preferred, that the stop be adjustable relative to thepiston.

Extending at least between the deflection control handle 116 and theneedle control handle 117 are components, including the proximal tubing13, the lead wire 15N, and thermocouple wires 9 in their protective,nonconducting tubing 11. These components covered by the guide tube 66pass through a shaft 70 for example, a braided shaft, whose proximal endis received in a rigid tubing 71, for example, a stainless steel tubing,affixed in a distal passage 72 in the distal end of the needle controlhandle 117 that communicates with the piston chamber 82. A shrink sleeve74 is mounted partially on the rigid tubing 71 and the shaft 70 toprovide strain relief.

The thermocouple wires 9 are provided for sensing temperature of the tipelectrode 2. The wires 9 along with the tubing 11, which may be made ofpolyimide, extend through the needle electrode assembly 132. In thedisclosed embodiment, the wires 9 and the tubing 11 extend through thelumen 13L of the proximal tubing 13 and the lumen 12L of the needleelectrode 12. Distal ends of the wires 9 and the tubing 11 arecoterminous with the distal end of the needle electrode 12. The portionof the tubing 11 extending through the lumen 12L may be affixed to theinner surface of the lumen 12L by adhesive sealant 135.

As shown in FIG. 9, the catheter includes luer hub 41 and 42 extendingoff the proximal end of the needle control handle 117. Connected to eachluer hub is a respective elongated flexible luer tubings 43 and 44 thatenter the proximal end of the needle control handle 117 via the luerconnector 86. The luer tubings 43 and 44 may be made of any suitablematerial, for example, polyimide. Surrounding the portion of each luertubing 43 and 44 extending between the luers 41 and 42 and the connectorluer 86 is a respective protective thick-walled outer shaft 49 whoseproximal and distal ends are sealed to the luers 41 and 42, and to theluer connector 86, respectively, by adhesive sealant, e.g., polyurethane135. A respective shorter tubing 46 constructed of any suitablematerial, for example, polyimide, may line the interior of the outershafts 49 to surround the distal portion of each luer tubing 43 and 44at or near the proximal end of the luer connector 86. A visual marker,e.g., a shrink sleeve 47, may be mounted on a selected tubing 43 or 44to distinguish one tubing from the other.

In the injection control handle 117, within the axial passage 85 of thepiston 84, as shown in FIGS. 6 and 6A, both luer tubings 43 and 44extend through the distal tubular portion 87 of the luer connector 86and into the proximal end 13P of the proximal tubing 13 of the needleelectrode assembly 132. In the illustrated embodiment of FIG. 6, theproximal end of the proximal tubing 13 is proximal of the proximal ends93P and 97P of the rigid tubing 93 and the protective tubing 97 which,in turn, are proximal of the proximal ends of the tubings 22 and 25.

The luer tubings 43 and 44 extend from their proximal ends in the luerhubs 41 and 42, respectively, to their distal ends at a predeterminedlocation along the longitudinal axis of catheter. In the disclosedembodiment, the predetermined location is within the needle controlhandle 117, as shown in FIG. 6A, where the luer tubings 43 and 44terminate at their distal ends and the first and second fluid pathways(arrows A and B) diverge into their relative inner and outer pathwaysalong the catheter. The first and second fluid pathways are isolatedfrom each other by a sealant, for example, polyurethane 135S, providedin the lumen 13L at the predetermined location. As shown in FIGS. 6B,6C, 6D and 6E, the polyurethane sealant 135S has passages formedtherethrough that communicate with the tubings 43 and 44 via theirdistal ends. The sealant 135S is also formed around at least lead wire15N for the needle electrode 12, and the tubing 11, for example, apolyimide tubing, that surrounds thermocouple wires 9.

For the second fluid pathway (arrows B), a notch opening 45 is formed inthe sidewall of the proximal tubing 13 so that the second fluid pathwayextending through the luer tubing 44 traverses the side wall of theproximal tubing 13 and enters the lumen 22L between the guide tubing 22and the outer surface of the proximal tubing 13. In contrast, the firstfluid pathway (arrows A) extends through the lumen of the tubing 43 andcontinues axially into the coaxial lumen 13L of the proximal tubing 13.

Because the lead wire 15N, and the thermocouple wires 9 (in theirprotective tubing 11) extend through the proximal tubing 13, they extendproximally past the deflection control handle 116 and into the injectioncontrol handle 117. However, because the interior space of the needlecontrol handle 117 is limited and occupied by the luer connector 86, thelead wire 15N, the thermocouple wires 9 along with the tubing 11 arererouted (distally) back through the injection control handle 117 andinto the deflection control handle 116 where they are connected to theelectrical connector 48. As shown in FIG. 6 and in more detail in FIG.8, these components exit the proximal end of the proximal tubing 13,where these components continue through the rigid tubular portion 87 ofthe luer connector 86 and then exit through an opening 30 formed in theside wall of the rigid tubular portion 87 toward its proximal end andenter a proximal end of a flexible protective tubing 32 that is coiledin the distal direction around the outer surface of the tubular portion87 and the protective tubing 97 toward the distal end of the needlecontrol handle 117. The protective tubing 32 passes distally through thedistal passage 72 (FIG. 6) and the shaft 70, remaining outside of butalongside the guide tubing 22. Inside the deflection control handle 116,the lead wire 15N, and the thermocouple wires 9 (along with the leadwires 15T for the tip electrode 2 and the 15R for the ring electrode)are connected to the electrical connector 48 at the proximal end of thedeflection control handle 116. As the needle electrode assembly 132 isextended and retracted, the coiled portion of the lead wire 15N and thethermocouple wires 9 in the needle control handle 117 is able toaccommodate movement of the proximal tubing 13 without breaking, whileadvantageously leaving the space-constrained proximal end of the handle117 for the luer connector 86.

The location of the divergence or the notch opening 45 along the secondfluid pathway is selectively positioned so as to be immediately distalto a proximal plunger member 23 so as to minimize the risk of trappingan air bubble. In the disclosed embodiment, the plunger member 23 is ashrink sleeve made of fluorinated ethylene propylene (FEP) and the guidetubing 22 is a made of composite material having an inner layer ofpolytetrafluoroethylene (PTFE). The plunger member 23 may also beformed, e.g., as a raised ring, as part of the outer surface of theproximal tubing 13. As such, the plunger member 23 forms a fluid-tightproximal end for the second fluid pathway (arrows B) defined by theguide tubing 22 around the needle assembly 132, while allowing theproximal tubing 13 to slide readily and smoothly relative to the guidetubing 22. To fixedly secure the plunger member 23 on the proximaltubing 13, adhesive sealant, such as polyurethane, is applied proximallyand distally at 135P and 135D, as illustrated in FIG. 6A.

As shown in FIG. 3A, the catheter includes the biosensor 16 which isused to determine the coordinates of the tip electrode 2, for example,to monitor the precise location of the distal end of the catheter in thepatient's body. The biosensor 16 is connected to the cable 16C whichextends through the lumen 124 of the tubing 19 of the deflection section114, and the central lumen 118 of the catheter body 112, and into thedeflection control handle 16 where wires of the cable 16C are connectedto the circuit board 64. The circuit board amplifies the signalsreceived from the sensor 16 and transmits them to a computer in a formunderstandable by the computer. The sensor 16 may comprise amagnetic-field-responsive coil, as described in U.S. Pat. No. 5,391,199,or a plurality of such coils, as described in International PublicationWO 96/05758. The plurality of coils enables the six-dimensionalcoordinates (i.e. the three positional and the three orientationalcoordinates) of the location sensor 77 to be determined. Alternatively,any suitable location sensor known in the art may be used, such aselectrical, magnetic or acoustic sensors. Suitable location sensors foruse with the present invention are also described, for example, in U.S.Pat. Nos. 5,558,091, 5,443,489, 5,480,422, 5,546,951, and 5,568,809,International Publication Nos. WO 95/02995, WO 97/24983, and WO98/29033, and U.S. patent application Ser. No. 09/882,125 filed Jun. 15,2001, entitled “Position Sensor Having Core with High PermeabilityMaterial,” the disclosures of which are incorporated herein byreference.

To use a catheter of the invention, an electrophysiologist may introducea guiding sheath and dilator into the patient, as is generally known inthe art. A guidewire may also be introduced for a catheter adapted forsuch use. Through the guiding sheath, the entire catheter body 112 canbe passed through the patient's vasculature to the desired location.Once the distal end of the guiding sheath reaches the desired location,the catheter can be advanced to expose the deflectable section 114. Thethumb control 56 of the control handle 116 may be manipulated as neededto deflect the deflectable section 114 and distal tip section 115 intoposition. After the distal tip electrode 2 is positioned in contact withtissue, electrical signals in the tissue may be sensed by anycombination of the tip electrode 2, the ring electrode 21 and the needleelectrode 12, with the signals being transmitted to the electricalconnector 48 in the deflection control handle 116 via lead wires 15T,15R and 15N, for example, to map the region. RF energy may be alsoapplied to the tip electrode 2 and/or the needle electrode 12 via thelead wires 15T and/or 15N to ablate the tissue. In that regard, fluidmay be introduced via the second fluid path (arrows B) which passesalong the catheter and exits the catheter at the distal end of the tipelectrode 2 to cool and displace blood from the area between theproximal exposed area of the needle electrode 12 and the distal face oftip electrode 2.

Additionally, the thumb control 106 of the injector control handle 117may be depressed distally to extend the needle electrode assembly 132and deploy the needle electrode 12 for piercing the tissue. RF energymay be applied to the lead wire 15N to energize the needle 55 to ablatethe tissue below the surface. In that regard, fluid may be introduced tocool the needle electrode 12. Moreover, the fluid may include saline forirrigation or other types of fluids for diagnostic or therapeuticpurposes. The thumb control 106 may be locked in the advanced positionby means of the detent feature on the thumb control 106 when the ball 75is moved distal of the vertical step 78V of the metal end cap 78.

When the thumb control 106 is released by application of a forcesufficient to push the ball proximal of the metal end cap 78, the needleelectrode 12 retracts into the tip electrode 2 and the catheter distaltip section 115 can be moved and relocated safely within the patient'sbody.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention. As understood by one of ordinary skill in the art, thedrawings are not necessarily to scale. Also, different features ofdifferent embodiments may be combined as needed or appropriate.Moreover, the catheters described herein may be adapted to apply variousenergy forms, including microwave, laser, RF and/or cryogens.Accordingly, the foregoing description should not be read as pertainingonly to the precise structures described and illustrated in theaccompanying drawings, but rather should be read consistent with and assupport to the following claims which are to have their fullest and fairscope.

What is claimed is:
 1. A catheter comprising: an elongated catheterbody; a distal tip section having a tip electrode with a distal end; aneedle electrode assembly extending through at least the elongatedcatheter body and the tip electrode, the needle electrode assembly beinglongitudinally movable relative to the catheter body and distal tipsection into an extended position and a retracted position, the needleelectrode assembly including a needle electrode; an injection controlhandle proximal of the catheter body configured to move the needleelectrode assembly into the extended position and the retractedposition; a fluid path B extending through at least the catheter bodyand having a distal exit at the distal end of the tip electrode; and afluid path A extending through at least the catheter body and having adistal exit at a distal end of the needle electrode assembly, whereinthe fluid path B and the fluid path A are isolated from each other, andwherein the fluid path B has a proximal portion that extends through theneedle electrode assembly, a distal portion that extends outside of theneedle electrode assembly, and a mid-portion that connects the proximalportion and the distal portion and traverses a side wall of the needleelectrode assembly.
 2. The catheter of claim 1, wherein the needleelectrode assembly has an elongated proximal tubing extending throughthe catheter body.
 3. The catheter of claim 1, further comprising aneedle centering insert, wherein the needle centering insert has aneedle passage through which needle electrode extends.
 4. The catheterof claim 3, wherein an inner surface of the insert lining the needlepassage has a cross-section with a smaller diameter and a largerdiameter.
 5. The catheter of claim 4, wherein portions with the smallerdiameter support the needle electrode assembly in the needle passage. 6.The catheter of claim 4, wherein portions with the larger diameterprovide axial grooves through the needle passage between the innersurface of the insert and an outer surface of the needle electrodeassembly.
 7. The catheter of claim 1, wherein the mid-portion is definedby preformed polyurethane.
 8. The catheter of claim 1, furthercomprising a guide tubing surrounding the needle electrode assemblyalong its length.
 9. The catheter of claim 1, wherein the needleelectrode assembly has an outer surface and includes a plunger member onthe outer surface proximally of the mid-portion of the fluid path B. 10.The catheter of claim 9, wherein the plunger member comprises a shrinksleeve.
 11. The catheter of claim 3, wherein the insert has a proximalend with at least one indented formation.
 12. The catheter of claim 11,wherein the at least one indented formation is configured to providefluid communication between the fluid path B and at least one axialgroove extending between the insert and the needle electrode assembly.13. A catheter comprising: an elongated catheter body; a distal tipsection having a tip electrode with a distal end, the tip electrodehaving a needle channel; a needle electrode assembly having a proximalportion extending through at least a lumen in the elongated catheterbody and a distal portion extending through the tip electrode, theneedle electrode assembly being longitudinally movable relative to thecatheter body and distal tip section into an extended position and aretracted position; an injection control handle proximal of the catheterbody configured to move the needle electrode assembly into the extendedposition and the retracted position; and a fluid path B extendingthrough at least the catheter body and having a distal exit at thedistal end of the tip electrode, wherein the fluid path B has a proximalportion that extends through the needle electrode assembly, a distalportion that extends between the needle electrode assembly and a guidetube surrounding the needle electrode assembly, and a mid-portion thatconnects the proximal portion and the distal portion and traverses aside wall of the needle electrode assembly.
 14. The catheter of claim13, further comprising: a fluid path A extending through at least thecatheter body and having a distal exit at a distal end of the needleelectrode assembly, wherein the fluid path A and the fluid path B areisolated from each other.
 15. The catheter of claim 14, wherein thefluid path A passes through the needle electrode assembly.
 16. Thecatheter of claim 14, wherein the proximal portion of the needleelectrode assembly includes a proximal tubing and the distal portion ofthe needle electrode assembly includes a needle electrode, and the fluidpath A passes through the proximal tubing and the needle electrode. 17.A catheter comprising: an elongated catheter body; a distal tip sectionhaving a tip electrode with a distal end, the tip electrode having aneedle channel and a needle centering insert, the needle centeringinsert having a needle passage and being positioned in the needlechannel of the tip electrode; a needle electrode assembly having aproximal portion extending through at least a lumen in the elongatedcatheter body and a distal portion extending through the needle passageof the insert, the needle electrode assembly being movable along alongitudinal axis relative to the catheter body and distal tip sectioninto an extended position and a retracted position; and an injectioncontrol handle proximal of the catheter body configured to move theneedle electrode assembly into the extended position and the retractedposition, wherein an inner surface of the needle centering insert has across-section with a smaller diameter and a larger diameter, thecross-section being perpendicular to the longitudinal axis, and whereinthe needle centering insert is configured to guide the distal portion ofthe needle electrode assembly.